As a small change in a person's dna can cause a genetic disorder

Affirmative, that is correct.

A genetic disorder is nothing more than an abnormal occurrence in a genome, which means that if you change DNA you'll change the genome, and if the change isn't acceptable, genetic disorders can occur easily.

Genetic disorders is a fun field within genetics, and it isn't easy. The functioning of a gene might be an easy concept now a days, but we haven't mastered it. For example, it's not like maths:

- Somebody comes up with a new, unsolved problem, and tries to solve it, and while doing that, the person can create laws, theorems, equations, etc.

Once you come up against a genetic disorder (you can't just create a genetic disorder to study it) you have to study the genetic disorder itself, what caused it and why.

Hope it helped,

BioTeacher101

the answer to your question is tooth decay.